Print pmove->cmd.msec, changed genscript parsing method

The pmove->cmd.msec is needed by genscript.  genscript is modified slightly to
accomodate the new way of executing scripts in SteamPipe Half-Life.  More
details should be available in the documentation.

Some minor refactorings are also done for genscript.
Added --append and --prepend to genscript
Fixed values of forwardmove and sidemove when newly ducked
Updated doc about script execution, added month to date